[bahy-lat-er-uh l]


pertaining to, involving, or affecting two or both sides, factions, parties, or the like: a bilateral agreement; bilateral sponsorship.
located on opposite sides of an axis; two-sided, especially when of equal size, value, etc.
Biology. pertaining to the right and left sides of a structure, plane, etc.
Chiefly Law. (of a contract) binding the parties to reciprocal obligations.
through both parents equally: bilateral affiliation.Compare unilateral(def 7).


Informal. a bilateral agreement, especially regarding international trade.

Origin of bilateral

First recorded in 1765–75; bi-1 + lateral
Related formsbi·lat·er·al·ism, bi·lat·er·al·ness, nounbi·lat·er·al·ly, adverb Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Related Words for bilateral

mutual, reciprocal, respective, two-sided

Examples from the Web for bilateral

Contemporary Examples of bilateral

Historical Examples of bilateral

  • This is, in substance, an evasion of the bilateral provision in the constitution.

  • The first three have bilateral, the last has radial symmetry.

    Form and Function

    E. S. (Edward Stuart) Russell

  • Are not almost all brains a little wanting in bilateral symmetry?

    Over the Teacups

    Oliver Wendell Holmes, Sr.

  • In rare instances the eruption has been observed to be bilateral.

    Essentials of Diseases of the Skin

    Henry Weightman Stelwagon

  • This is a bilateral contract, and either may sue the other for a breach.

    Commercial Law

    Samuel Williston, Richard D. Currier, and Richard W. Hill

British Dictionary definitions for bilateral



having or involving two sides
affecting or undertaken by two parties; mutuala bilateral treaty
denoting or relating to bilateral symmetry
having identical sides or parts on each side of an axis; symmetrical
sociol relating to descent through both maternal and paternal lineageCompare unilateral (def. 5)
British relating to an education that combines academic and technical courses
a bilateral meeting
Derived Formsbilaterally, adverb
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for bilateral

"having two sides," 1775, from bi- + lateral. Related: Bilaterally.

Online Etymology Dictionary, © 2010 Douglas Harper

bilateral in Medicine




Having or formed of two sides; two-sided.
Having or marked by bilateral symmetry.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.